This R21 application covers a secondary analysis of a case control study of the relation of BAC to crash involvement that was undertaken between June of 1997 and September of 1998 in Long Beach, California and between September 1998 and September 1999 in Fort Lauderdale, Florida. Drivers in 2,871 crashes were interviewed and breath tested together with two controls for each crash involved driver. Overall, 14,985 drivers were approached. Very high participation rates were achieved (97.6% for control drivers and 90.5% of crash involved drivers). The proposed reanalysis will include six studies designed to improve the specification of the resulting alcohol/crash risk model, identify specific risk levels for subgroups of drivers such as females and underage drivers; determine the extent that loss of control of drinking is associated with crash involvement; determine the population based attributable risk of crash involvement; the effectiveness of the passive sensor for drivers at various BACs and determine the relationship of BAC to crash responsibility. [unreadable] [unreadable]